This invention relates to chromatography and more specifically to chromatographic columns, methods of making chromatographic columns and methods of using chromatographic columns.
The use of chromatographic columns for the analysis and separation of substances from mixtures has long been known. One type of such column is a disposable column intended for limited use and accordingly manufactured with economy in mind.
One prior art disposable column has been available in commerce for a substantial period of time. It is manufactured of inexpensive plastics and designed to be easily assembled by filling the body of the column with the desired packing and then welding the open end or ends closed. The prior art chromatographic column has the disadvantage of being more costly then desirable to assemble and being more subject to leaks under pressure then desirable.
Accordingly, it is an object of the invention to provide a novel chromatographic column.
It is a further object of the invention to provide a novel method of manufacturing and using a chromatographic column.
It is a still further object of the invention to provide a novel chromatographic column that can be filled through an open end and then the open end closed with simple linear motion.
It is a still further object of the invention to provide a novel chromatographic column with a snap-on end.
It is a still further object of the invention to provide a novel inexpensive disposable chromatographic column.
In accordance with the above and further objects of the invention, a chromatographic column is formed of a relatively inexpensive material, filled with the desired packing material and then closed at one end without welding and nonetheless forming a seal that can withstand substantial pressure. In the preferred embodiment, the end is applied with relatively simple substantially linear motion so as to be capable of being implemented in an automated fashion and snaps in place to provide an adequate seal against internal pressures.
For this purpose, the column is formed of an inexpensive plastic with the tubular body portion and one end with one port being molded as a single piece. A snap-on end piece is also molded as a single piece with a port as an integrally molded part of it and snapped onto the tubular body portion with an interference fit adequate to resist leaks at a value above the rated value of the column. Preferably one of the end piece and the open end of the body of the column has snap members that engage detents on the other of the open end of the body and the end piece to hold the two together with adequate force about a tapered connection to form an adequate seal to resist the pressure built up on the column during use. The number of snaps and dimensions are selected to permit the appropriate inexpensive plastic to withstand the stress in use. In the preferred embodiment, the column is made substantially of polypropylene because it is inexpensive and sufficiently inert to withstand usage with normal solvents for a limited number of uses.
In molding the snap-on end and in molding the body a plurality of cantilever members are molded onto one of the body and the snap-on end and a plurality of detents are molded onto the other of the body and snap-on end. The number of detents and cantilever members are selected to maintain the combined bending stress of the cantilever members being bent outwardly over the catch and the tensile stress below the failure of the material comprising the cantilever members. The thickness of the material, the area connected the cantilever members to the rest of the end piece and the type of material are selected in conjunction with the height of the detent necessary to hold the cantilevers with the necessary force for an interference fit without excessively bending the cantilever members while being moved over the detents.
From the above description, it can be understood that the method and apparatus of this invention has several advantages, such as: (1) it is economical in terms of its fabricating materials; (2) it is inexpensive to assemble; (3) it can be assembled readily in an automated process; and (4) it can be easily formed of relatively inexpensive materials.